JP4619853B2 - Uniform thickness polyimide film and manufacturing method thereof - Google Patents

Description

  The present invention relates to a polyimide film with improved thickness unevenness and a method for producing the same, and in particular, a support for an electric wiring board on which a metal foil or a metal thin film represented by copper foil is laminated, and a cover for protecting a flexible printed circuit. The present invention relates to a polyimide film suitable for use as a lay film and a method for producing the same.

  Polyimide film has high heat resistance and high electrical insulation, so it is used in a wide range of industrial fields as an electrical insulation material that requires heat resistance, especially as a support for electrical wiring boards laminated with copper foil. Has been. When a polyimide film is used as a support for an electrical wiring board, a heat-resistant flexible printed circuit board can be manufactured, and solder can be used to connect electrical components (such as ICs) and copper foil. The product can be reduced in size and weight. Therefore, the use of the flexible printed circuit board which used the polyimide film as a support body of an electrical wiring board spreads, and the demand of a polyimide film is growing. However, with the diversification of uses of electrical wiring boards and higher quality of electrical wiring boards (for example, higher density of wiring, etc.), there is a demand for improvement in performance and workability improvement of polyimide film as an electrical insulating support. Has increased. In particular, when a polyimide film is used as a support for an electric wiring board in a heat-resistant flexible printed circuit (FPC), it is necessary to bond the polyimide film and a metal foil or a metal thin film with a heat-resistant adhesive in the manufacture of FPC. However, when the polyimide film has uneven thickness, when the heat-resistant adhesive is applied, uneven application of the heat-resistant adhesive, repelling, and the like occur, resulting in a decrease in yield.

In Patent Document 1, a polyimide film having a width of 35 μm to 200 μm and a height of 0.1 to 1.0 μm generated in the longitudinal direction, and the number of the streaks is 40 or less per 1000 mm is manufactured. However, it is described that the residence time, pressure loss, and temperature of the polymer in the die are controlled within a specific range. However, the method described in this document is not very effective in reducing the stripe-like thickness unevenness at a film width of 5 to 10 mm, which is generated due to the roughness unevenness of the inner wall of the pipe or the inner wall of the base, to a yield of FPC or the like There is no effect to improve.
JP 2001-162631 A

  An object of the present invention is to provide a polyimide film having a small thickness non-uniformity and particularly excellent in the use of a support for an electric wiring board and a coverlay film for FPC protection, and a method for producing the same.

  As a result of intensive studies to achieve the above object, the inventors of the present invention supplied the polyamic acid solution through a pipe having a pipe inner wall surface roughness of 1.0 μm or less as a flow path, and the surface roughness of the inner wall of the die. A gel film is formed by casting a polyamic acid solution on a support from a die having a thickness of 0.1 μm or less, and then imidizing the polyamic acid in the gel film results in a thickness variation of 1.0 μm in the width direction. It has been found that a polyimide film having a width of 500 mm or more can be produced industrially advantageously, and is characterized in that the stripe-shaped thickness unevenness within the range of 10 mm or less is 0.7 μm or less. When a metal foil or metal thin film is bonded to the resulting polyimide film with a heat-resistant adhesive, problems such as uneven application of the heat-resistant adhesive and repellency may occur. It found that it is much improved compared.

That is, the present invention
(1) A polyimide film having a width of 500 mm or more, wherein the thickness unevenness in the width direction of the polyimide film is 1.0 μm or less and the stripe-like thickness unevenness within a range of 10 mm or less is 0.7 μm or less. ,
(2) The polyimide film according to the above (1), in which the stripe-shaped thickness unevenness is 0.2 μm or less, and (3) by casting a polyamic acid solution supplied using a pipe as a flow path from a die onto a support. In the method for producing a polyimide film by forming a gel film and then imidizing the polyamic acid in the gel film, the surface roughness of the inner wall of the pipe is 1.0 μm or less, and the surface roughness of the inner wall of the die is A method for producing a polyimide film, which is 0.1 μm or less,
About.

The polyimide film of the present invention has a small thickness unevenness, for example, problems such as uneven application of the heat-resistant adhesive and repelling that occur when the film is bonded to a metal foil or a metal thin film by a heat-resistant adhesive compared to conventional polyimide films. It is remarkably improved, and in particular, it is excellent for use as a support for an electric wiring board and a coverlay film for FPC protection.
Further, according to the production method of the present invention, a polyimide film with improved thickness unevenness can be produced stably and industrially advantageously.

The polyimide film of the present invention has a width unevenness of 1.0 mm or less in the width direction of the polyimide film, and a stripe-shaped thickness unevenness within a range of 10 mm or less is 0.7 mm or less. It is the above polyimide film.
The thickness unevenness is such that a film having a width of 500 mm or more excluding the edge 10 mm is fed by a film feeding device at a feeding speed of 1.5 m / min, and a wide range electronic micrometer K301 manufactured by Anritsu Co., Ltd. A thickness chart is recorded using a table type automatic equilibrium recorder, and the difference between the maximum value and the minimum value in the total width of the film and the width of 5 to 10 mm of each part is calculated from the recorded result. In addition, streaky thickness unevenness refers to thickness unevenness within a range of 10 mm or less in width (especially 5 to 10 mm in width).

In the present invention, the stripe-like thickness unevenness within the range of the width of 10 mm or less is 0.7 μm or less, preferably 0.3 μm or less. The lower limit is not critical but is usually 0.1 μm.
Further, the thickness unevenness within a full width range of 500 mm or more excluding the end portion 10 mm is 1.0 μm or less, preferably 0.8 μm or less. The lower limit is not critical but is usually 0.3 μm.

  The polyimide film of the present invention supports a polyamic acid solution supplied through a pipe having a pipe inner wall surface roughness of 1.0 μm or less as a flow path from a die having a die inner wall surface roughness of 0.1 μm or less. It is manufactured by casting a gel film by casting (gel film forming step) and then imidizing the polyamic acid in the gel film (polyimide forming step).

(Piping)
The piping used for the production of the polyimide film of the present invention is not particularly limited as long as the surface roughness of the inner wall of the piping is 1.0 μm or less, which is a piping that becomes a flow path until the polyamic acid solution reaches the die. A pipe whose inner wall has a surface roughness of 1.0 μm or less is subjected to a polishing process such as mechanical polishing on the inner wall of a known pipe used in the solution casting method, etc., so that the surface roughness is 1.0 μm or less. It is manufactured by doing. The “surface roughness” is measured using a surface roughness measuring device Surf Test 401 manufactured by MITUTOYO Co., Ltd.

(Base)
The die used for producing the polyimide film of the present invention is not particularly limited as long as the surface roughness of the inner wall of the die is 0.1 μm or less. When the surface roughness of the inner wall of the die exceeds 0.1 μm, the stripe thickness unevenness within the width of 10 mm or less on the surface of the polyimide film exceeds 0.7 μm, and the width excluding the end 10 mm is 500 mm or more. The thickness unevenness within the range of the entire width exceeds 1.0 μm. Moreover, in this invention, it is preferable that the surface roughness of the said inner wall of a nozzle | cap | die is 0.01-0.1 micrometer. By setting the surface roughness within this preferred range, abnormal retention and adhesion of the polymer can be prevented.
A die having a surface roughness of the inner wall of the die of 0.1 μm or less is manufactured by polishing the inner wall of a known slitted die used in a solution casting method or the like to bring the surface roughness to 0.1 μm or less. Is done. Examples of the polishing treatment include mechanical polishing.
The “surface roughness” is measured using a surface roughness measuring device Surf Test 401 manufactured by MITUTOYO Co., Ltd.

（上記式［Ｉ］においてＲ１は少なくとも１個の芳香族環を有する４価の有機基で、その炭素数は２５以下であるものとし、Ｒ１に結合する２つのカルボキシル基の夫々はＲ１における芳香族環のアミド基が結合する炭素原子とは相隣接する炭素原子に結合しているものであり、またＲ２は少なくとも１個の芳香族環を有する２価の有機基で、その炭素数は２５以下であるものとし、アミノ基はＲ２における芳香族環の炭素原子に結合しているものである。） (Polyamide acid solution)
The polyamic acid solution used as a raw material in the present invention is not particularly limited as long as the polyamic acid is dispersed and dissolved in an organic solvent.
The said polyamic acid is a precursor of a polyimide, and contains the structural unit shown by following formula [I].

(In the above formula [I], R1 is a tetravalent organic group having at least one aromatic ring, the carbon number of which is 25 or less, and each of the two carboxyl groups bonded to R1 is an aromatic group in R1. The carbon atom to which the amide group of the aromatic ring is bonded is bonded to the adjacent carbon atom, and R2 is a divalent organic group having at least one aromatic ring, and the carbon number is 25 And the amino group is bonded to the carbon atom of the aromatic ring in R2.)

The polyamic acid is produced by polymerizing aromatic tetracarboxylic acids and aromatic diamines according to a conventional method.
Specific examples of the aromatic tetracarboxylic acids include pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,3 ′, 3,4′-biphenyltetracarboxylic acid, 3,3 ', 4,4'-benzophenone tetracarboxylic acid, 2,3,6,7-naphthalenedicarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) ether, pyridine-2,3,5,6- Tetracarboxylic acids and their amide-forming derivatives are mentioned. In the production of polyamic acid, these acid anhydrides are preferably used.

  Specific examples of the aromatic diamines include paraphenylenediamine, metaphenylenediamine, benzidine, paraxylylenediamine, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, and 4,4′-diaminodiphenyl. Sulfone, 3,3′-dimethyl-4,4′-diaminodiphenylmethane, 1,5-diaminonaphthalene, 3,3′-dimethoxybenzidine, 1,4-bis (3methyl-5aminophenyl) benzene and their Examples include amide-forming derivatives. Among these, it is preferable to contain at least paraphenylenediamine.

  Specific examples of the organic solvent include organic polar amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, and these organic solvents are used alone or Two or more types may be used in combination, or these may be used in combination with a non-solvent such as benzene, toluene or xylene. The polyamic acid solution has a solid content of 5 to 40% by weight, preferably 10 to 30% by weight, and has a viscosity of 500 to 20000 poise, preferably 1000 to 10,000 poise as measured by a Brookfield viscometer. It is preferable because stable liquid feeding is possible. The polyamic acid in the organic solvent solution may be partially imidized and may contain a small amount of an inorganic compound.

The polyamic acid solution is obtained by polymerizing the aromatic tetracarboxylic acid and the aromatic diamine in the organic solvent.
In the present invention, the aromatic tetracarboxylic acids and the aromatic diamines are polymerized in such a proportion that their respective mole numbers are approximately equal, or one of them is within a range of 10 mol%, preferably 5 mol%, relative to the other. It may be blended in excess. The polymerization reaction is continuously carried out for 10 minutes to 30 hours in the temperature range of 0 to 80 ° C. with stirring and / or mixing in an organic solvent. If necessary, the polymerization reaction is divided or the temperature is increased or decreased. It doesn't matter. Although there is no restriction | limiting in particular in the addition order of both reactants, It is preferable to add aromatic tetracarboxylic acid in the solution of aromatic diamines. Further, vacuum degassing may be performed during the polymerization reaction, and vacuum degassing during the polymerization reaction is an effective method for producing a good quality organic solvent solution of polyamic acid. Further, before the polymerization reaction, a small amount of end-capping agent may be added to the aromatic diamines to control the polymerization reaction.

  When imidization is performed by a chemical ring closure method, a ring closure catalyst and a dehydrating agent are blended in the polyamic acid solution prior to forming the polyamic acid solution into a gel film.

  Specific examples of the ring-closing catalyst include aliphatic tertiary amines such as trimethylamine and triethylenediamine, and heterocyclic tertiary amines such as isoquinoline, pyridine and β-picoline, which are selected from heterocyclic tertiary amines. It is preferred to use at least one amine.

The content of the ring-closing catalyst with respect to the polyamic acid is preferably within the range of the following formula.
[Equation 1]
0.5 <content of cyclization catalyst (mole) / polyamic acid content (mole) <8

  Specific examples of the dehydrating agent include aliphatic carboxylic acid anhydrides such as acetic anhydride, propionic anhydride and butyric anhydride, and aromatic carboxylic acid anhydrides such as benzoic anhydride, among which acetic anhydride and / or Benzoic anhydride is preferred.

The content of the dehydrating agent relative to the polyamic acid is preferably within the range of the following formula.
[Equation 2]
0.1 <content of dehydrating agent (mol) / polyamic acid content (mol) <4
In addition, a small amount of inorganic powder may be added to the polyamic acid for imparting slipperiness of the film, or a gelation retarder such as acetylacetone may be used in the polyamic acid solution in addition to the ring closure catalyst and the dehydrating agent. Good.

  The polyamic acid solution is blended with the ring-closing catalyst and the dehydrating agent by mixing the polyamic acid solution, the ring-closing catalyst and the dehydrating agent with a rotary mixer, or while statically mixing the polyamic acid solution while feeding the polyamic acid solution to the static mixer. Examples include a method of injecting a ring-closing catalyst and a dehydrating agent immediately before the machine, a method of casting an organic solvent solution of polyamic acid on a support, and then a method of contacting the ring-closing catalyst and the dehydrating agent. From the viewpoint of the content and uniform dispersibility, it is preferable to mix the ring-closing catalyst and the dehydrating agent in the polyamic acid solution by mixing with a mixer. When a mixer is used, it is preferable to adjust the solid content concentration and the temperature so that the viscosity of the mixer is 100 to 10,000 poise. The resulting mixture is preferably kept at a low temperature (for example, within a range of −20 ° C. to + 5 ° C.) because the polyamic acid undergoes a thermal ring-closing reaction and has a property that the viscosity becomes extremely high and cannot be discharged from the die. .

(Gel film forming process)
In the gel film forming step, the gel film is formed by casting the polyamic acid solution supplied using the pipe as a flow path from the die onto a support. For example, the polyamic acid solution is cast from a base with slits onto a support (for example, a rotating drum or a belt) that moves in a predetermined direction to form a film, and then heated and dried on the support. A gel film is used. The gel film produced in this step is preferably a gel film having self-supporting property in which a part of the polyamic acid in the film is imidized. The gel film having self-supporting property can be produced by heating and drying the polyamic acid solution when it is formed into a film or after it is formed.

  The gel film obtained in the gel film forming step may be stretched using a stretching roll, and a known stretching means is appropriately employed for the stretching. The stretching temperature, the stretching ratio, etc. are not particularly limited.

(Polyimide film formation process)
In a polyimide film formation process, the polyamic acid in a gel film is imidated and a polyimide film is manufactured. Since the method of imidizing polyamic acid is a well-established technique, these known techniques can be appropriately employed. For example, a method of imidization by a ring-closing reaction can be mentioned, and more specifically, a thermal ring-closing method using heat, a chemical ring-closing method using a dehydrating agent and a catalyst, and the like can be given. In the present invention, any of the above-mentioned ring closure methods may be employed, but the chemical ring closure method has a self-holding property although it requires equipment for containing a ring closure catalyst and a dehydrating agent in an organic solvent solution of polyamic acid. A gel film is preferable in that it can be obtained in a short time.

Hereinafter, an example of a preferred embodiment of the present invention will be described.
A support that moves a polyamic acid solution supplied through a pipe having a surface roughness of the inner wall of the pipe of 1.0 μm or less in a predetermined direction through a base having a slit having a surface roughness of the inner wall of the base of 0.1 μm or less. A gel film made of polyamic acid is produced by casting on a rotating drum (for example, a rotating drum or belt) and then drying on a support. During drying, a part of the polyamic acid on the support undergoes a thermal ring-closing reaction to imidize to form a gel film having self-supporting properties. More specifically, the gel film is heated to 30 to 200 ° C., preferably 40 to 150 ° C. by receiving heat from the support and / or receiving heat from a heat source such as hot air or an electric heater. A part of the acid undergoes a ring-closing reaction, and it becomes self-supporting by drying volatile components such as the free organic solvent. The obtained gel film is peeled from the support. The support is a metal rotating drum or endless belt, and its temperature is controlled by a liquid or gaseous heat medium and / or by radiant heat from an electric heater or the like.

  The gel film peeled from the support is stretched in the traveling direction by regulating the traveling speed with a stretching roll. The stretching is preferably carried out at a temperature of 140 ° C. or less at a magnification of 1.05 to 1.9 times, preferably 1.1 to 1.6 times, more preferably 1.1 to 1.5 times.

  The gel film stretched in the running direction is preferably introduced into a tenter device, gripped at both ends in the width direction by the tenter clip, and stretched in the width direction while running with the tenter clip.

  Next, the gel film after the stretching treatment is dried in a drying zone. When heating with hot air, etc. in the drying zone, a nozzle that can exhaust used hot air (air containing solvent or wet air) is installed to prevent contamination of the used hot air in the drying zone. It is done. The hot air temperature in the drying zone is preferably in the range of 200 to 300 ° C. Further, not only hot air but also radiant heating may be used.

  The film dried in the drying zone is preferably further heat-treated. The heat treatment is performed using a known means such as hot air or an electric heater (for example, an infrared heater). The heat treatment conditions are preferably a treatment temperature of 250 to 500 ° C. and a treatment time of 15 seconds to 20 minutes. In the heat treatment, if the film is heated rapidly, the flatness is lost, and therefore it is preferable to select a heating method as appropriate. The heat-treated film is cooled and wound on a winding core. Then, the wound polyimide film is slit.

  In the polyimide film of the present invention, it is also preferable to blend different polymers for the purpose of increasing the strength, as long as the object of the present invention is not impaired. In addition, organic additives such as antioxidants, heat stabilizers, ultraviolet absorbers, light-shielding agents, and antistatic agents may be added to the extent that they are usually added. Since the polymer blending method and the additive adding method are well-established techniques, these techniques can be appropriately employed.

  Moreover, it is also preferable that the polyimide film of the present invention is subjected to adhesiveness or low heat recovery treatment such as plasma treatment, corona discharge treatment, and annealing treatment.

  The polyimide film obtained as described above has problems such as coating unevenness and adhesive repellency that occur when it is bonded to a metal foil or metal thin film with a heat-resistant adhesive, compared to conventional polyimide films. Therefore, it is excellent in the use of a support for an electric wiring board and a coverlay film for FPC protection.

[Measuring method of physical properties] The measuring method of each characteristic value in this example is as follows.
(1) Surface roughness of piping inner wall and base inner wall It measured using the surface roughness measuring device Surf Test 401 made from MITUTOYO.
(2) Film thickness unevenness Using a film feeding device, the film is fed at a feeding speed of 1.5 m / min, and a wide range electronic micrometer K301 manufactured by Anritsu Co., Ltd. and a table type automatic equilibrium recorder manufactured by JEOL The thickness chart was recorded, and the difference between the maximum value and the minimum value over the entire width of the film was calculated from the recorded result. For the stripe-like thickness unevenness, the maximum value of the thickness unevenness at a width of 10 mm or less was obtained.

Example 1
20.24 kg (0.1 kmol) of 4,4′-diaminodiphenyl ether was dissolved in 190.6 kg of dried N, N-dimethylacetamide, and the powdered pyromellitic dianhydride was purified while stirring at 20 ° C. 21.812 kg (0.1 kmol) was added little by little, and stirring was continued for 1 hour to obtain a transparent polyamic acid solution. This solution had a viscosity of 350 Pa · s at 20 ° C. On the other hand, calcium hydrogen phosphate having a median average diameter of 0.97 μm was added so as not to aggregate in the previously prepared polyamic acid solution so that the inorganic powder was 0.2% by weight with respect to the polymer solid content. To this polyamic acid solution, 2.5 mol of acetic anhydride with respect to the polyamic acid unit and 2.0 mol of pyridine with respect to the polyamic acid unit were mixed while cooling to −5 ° C. to obtain a polyamic acid organic solvent solution. This polyamic acid organic solvent solution is cooled to −10 ° C., and a fixed amount of pipe is supplied in a surface roughness of 0.3 μm, and a coating having a slit width of 1.3 mm, a length of 1940 mm, and a surface roughness of 0.1 μm The film was extruded from a hanger die, peeled off from the metal endless belt, stretched 1.3 times in the running direction at a temperature of 65 ° C., and then introduced into a tenter. Stretched 1.4 times in the width direction with a tenter, dried at 260 ° C for 40 seconds, then heat treated at 430 ° C for 1 minute, cooled in the cooling zone for 30 seconds, edge cut the film, A polyimide film original fabric having a thickness of 2000 mm and a thickness of 25 μm was obtained. When this raw material is obtained, the film thickness is measured in the width direction online, and the data is fed back to the slit die to adjust the gap between the slit dies. Adjusted as follows.
The stripe-shaped thickness unevenness of the obtained film with a width of 10 mm or less was 0.2 μm, and the thickness unevenness of the entire width was 1.0 μm.

(Example 2)
In 190.6 kg of dried N, N-dimethylacetamide, 14.002 kg (0.07 kmol) of 4,4′-diaminodiphenyl ether and 3.236 kg (0.03 kmol) of paraphenylenediamine were dissolved and stirred at 20 ° C. Then, 21.812 kg (0.1 kmol) of purified powdery pyromellitic dianhydride was added little by little, and stirring was continued for 1 hour to obtain a transparent polyamic acid solution. This solution had a viscosity of 350 Pa · s at 20 ° C. On the other hand, calcium hydrogen phosphate having a median average diameter of 0.81 μm was added to the polyamic acid solution prepared previously so that the inorganic powder was 0.15% by weight with respect to the polymer solid content so as not to aggregate. To this polyamic acid solution, 2.5 mol of acetic anhydride with respect to the polyamic acid unit and 2.0 mol of pyridine with respect to the polyamic acid unit were mixed while cooling to −5 ° C. to obtain a polyamic acid organic solvent solution. This organic solvent solution of polyamic acid is cooled to −10 ° C., and a fixed amount is supplied in a pipe having a surface roughness of 0.3 μm, and the slit width of the base is 1.3 mm, the length is 1940 mm, and the surface roughness is 0.1 μm. The gel film was extruded from a coat hanger die and cast on a metal endless belt at 90 ° C. to obtain a self-supporting gel film. The gel film was peeled from the metal endless belt, stretched 1.3 times in the running direction at a temperature of 65 ° C., and then introduced into a tenter. Stretched 1.4 times in the width direction with a tenter, dried at 260 ° C for 40 seconds, then heat treated at 430 ° C for 1 minute, cooled in the cooling zone for 30 seconds, edge cut the film, A polyimide film original fabric having a thickness of 2000 mm and a thickness of 12.5 μm was obtained. When this raw material is obtained, the film thickness is measured in the width direction online, and the data is fed back to the slit die to adjust the gap between the slit dies. Adjusted as follows.
The resulting film had a stripe-like thickness unevenness of 0.2 μm or less at a width of 10 mm or less, and the thickness unevenness of the entire width was 0.8 μm.

(Example 3)
In 200.6 kg of dried N, N-dimethylacetamide, 20.0.0024 kg (0.1 kmol) of 4,4′-diaminodiphenyl ether was dissolved, and purified at 20 ° C. while purifying powdered pyromellitic dianhydride 21.812 kg (0.1 kmol) was added little by little, and stirring was continued for 1 hour to obtain a transparent polyamic acid solution. This solution had a viscosity of 350 Pa · s at 20 ° C. On the other hand, calcium hydrogen phosphate having a median average diameter of 0.97 μm was added so as not to aggregate in the previously prepared polyamic acid solution so that the inorganic powder was 0.2% by weight with respect to the polymer solid content. To this polyamic acid solution, 2.5 mol of acetic anhydride with respect to the polyamic acid unit and 2.0 mol of pyridine with respect to the polyamic acid unit were mixed while cooling to −5 ° C. to obtain a polyamic acid organic solvent solution. This organic solvent solution of polyamic acid is cooled to −10 ° C., and a fixed amount is supplied in a pipe having a surface roughness of 0.3 μm, and the slit width of the base is 1.3 mm, the length is 1940 mm, and the surface roughness is 0.1 μm. The gel film was extruded from a coat hanger die and cast on a metal endless belt at 90 ° C. to obtain a self-supporting gel film. The gel film was peeled from the metal endless belt, stretched 1.3 times in the running direction at a temperature of 65 ° C., and then introduced into a tenter. Stretched 1.4 times in the width direction with a tenter, dried at 260 ° C for 40 seconds, then heat treated at 430 ° C for 1 minute, cooled in the cooling zone for 30 seconds, edge cut the film, A polyimide film original fabric having a thickness of 2000 mm and a thickness of 10 μm was obtained. When this raw material is obtained, the film thickness is measured in the width direction online, and the data is fed back to the slit die to adjust the gap between the slit dies. Adjusted as follows.
The stripe-shaped thickness unevenness of the obtained film with a width of 10 mm or less was 0.2 μm, and the thickness unevenness of the entire width was 1.0 μm.

(Comparative Example 1)
A film was formed in the same manner as in Example 1 except that a T die having a surface roughness of 0.2 μm was used instead of the coat hanger die. The resulting film had a stripe-like thickness unevenness of 0.2 μm or less at a width of 10 mm or less, and the thickness unevenness of the entire width was 1.2 μm.

(Comparative Example 2)
A film was formed in the same manner as in Example 1 except that a T die having a surface roughness of 0.4 μm was used instead of the coat hanger die. The stripe-shaped thickness unevenness of the obtained film with a width of 10 mm or less was 0.5 μm, and the thickness unevenness of the entire width was 1.2 μm.

(Comparative Example 3)
A film was formed in the same manner as in Example 1, except that a pipe having a surface roughness of 1.2 μm on the inner wall of the pipe for quantitatively supplying the obtained organic solvent solution of polyamic acid was used. The stripe-shaped thickness unevenness of the obtained film with a width of 10 mm or less was 0.8 μm, and the thickness unevenness of the entire width was 1.3 μm.

The properties of the films obtained in Examples 1-3 and Comparative Examples 1-3 are summarized in Table 1 below.

According to the present invention, it is possible to provide a polyimide film having a small thickness non-uniformity and particularly excellent in the use of an electric wiring board support and an FPC protection coverlay film, and a method for producing the same.

Claims (2)

Polyimide film by the polyamic acid solution supplied as the flow path leading up to the base of the pipe, the gel film was formed by casting on a support from a die, and then imidizing the polyamic acid in the gel film In the method of manufacturing a polyimide film, the surface roughness of the inner wall of the pipe is 1.0 μm or less, and the surface roughness of the inner wall of the die is 0.1 μm or less. 2. The production according to claim 1, wherein the thickness unevenness in the width direction of the polyimide film is 1.0 μm or less, and the stripe-like thickness unevenness within a range of 10 mm or less is 0.3 μm or less. A polyimide film having a width of 500 mm or more obtained by the method .